Erosive resistant ferrous alloy



Patented Oct. 25, 1927.

UNITED STATES PATENT OFFICE..-

CHARLES B. JACOBS, OF WILMINGTON, DELAWARE, ASSIGNOR TO E. I. DU PONT DE NEMOURS & COMPANY, OF WILMINGTON, DELAWARE, A CORPORATION OF DELA- WARE.

EROSIVE RESISTANT FERROUS ALLOY.

No Drawing.

This invention relates to a ferrous alloy, and more particularly to an alloy which may be considered as a cast iron of a peculiarly desirable and new character, it having the desirable characteristics of cast iron,

such as ability to be simply and inexpensively made and readily cast, but in addition being characterized by extreme hardness,

fineness of grain, and great strength. It is the general Object of the invention to provide an alloy of the desirable character indicated.

I have found that the addition of.relatively high percentages of manganese as compared to those generally present in cast iron gives a variety of iron castings having the properties indicated above. Based on this discovery, the new alloy contains iron, carbon in an amount characteristic of cast iron (in excess of 2%) and manganese in an amount between 3 and 15%, preferably between 9 and 10%. It is readily produced ina cupola according to the procedure generally used in making cast iron.

The new alloy is, as stated, extremely hard and fine-grained and, in addition to being hard like chilled iron, is stronger than either chilled ironor grey cast iron, it having a modulus of rupture of from 40,000 to 50,000 pounds per square inch, depending on its content of manganese, the modulus increasing with the manganese content (but 5% of manganese being about the maximum). Its extreme toughness and tenacity is shown by the fact that test bars containingeven'as high as 10.5% manganese took a permanent set under transverse stress before breaking. Under the same character of stress ordinary cast iron or chilled cast 40 ir'on breaks with a sharp break. The property of great-' hardness, combined with toughness, makes the alloy particularly suitable for use in the construction of wearing parts such as liner plates, plows, rabble blades, crushing rolls, stamp shoes, grinding plates for attrition mills and pulverizers, and in general makes it suitable for a large variety of uses where great hardness, combined with toughness and tenacity, is essenm tial to the life and efliciency of the wearing arts. p The total carbon content of the alloy is greater than 2%, most of the carbon being in the combined form. As indicated, considerable variation in the percentage 0 Application filed January 11, 1923. Serial No. 612,016.

manganese is permissible, variations in the percent-age producing various degrees of strength and of resistance to erosion; and it is possible to so design and control the composition of this alloy, or new variety of cast iron, as to make the alloy particularly suitable for particular purposes. Typical examples of the efiect of varying the manganese content, other elements remaining All of the above mixtures make very close grained castings, considerably harder and tougher than ordinary grey iron, which usually show a modulus of rupture of from 33,000 to 39,000# 'with little or no deflect-ion. The high manganese irons have considerable deflection.

The preferable procedure for making alloys of the present invention is to add to a regular cupola mixture, such for example as used in making an ordinary grey cast iron, a quantity of ferro-manganese, or pure manganese, suflicient to produce in the cast metal the desired manganese content, and to operate the cupola, and cast, in the usual manner. No special precautions in the operation of the cupola or in the molding are required. The function of'the manganese in the cupola operation is to convert the greater portion of the graphitic carbon of the iron into a combined carbon in the form of a double carbide of iron and manganese (MnFe) C. This double carbide is extremely hard and its uniform distribution as such throughout the casting, dissolved in a matrix of iron, hardens and toughens the Whole structure of the casting.

Various additions of other elements to the alloy, for example to give special properties and characteristics especially adapting the alloy to particular uses, may be made without sacrifice of the desirable physical properties f characterising the alloy in general, I having IOU found that considerable latitude in making up the cupola charges is permissible. For example, chromium in quantities of from, say, 1 to 5% (the percentage of iron being correspondingly reduced) may be added to steel scrap or special grades of pig iron, with high or low silicon may be added to the cupola mixture. 1

Since the addition of manganese to cast iron eliminates sulphur to a large extent, the sulphur content or the alloy is extremely low. This too tends to strengthen and toughen the iron, especially under elevated temperatures, since high sulphur irons are Weak, especially at elevated temperatures.

Merely for the purpose of illustration and comparison I may note that two alloys 1 have made, typical of the present invention,

gave the following analysis (percent) (a) manglanese 10.17, combined carbon 2.41, grap itic carbon 1.20, (b) manganese 9.08, combined carbon 2.11, graphitic carbon 1.77, the remainder being of course iron in both cases except for suchimpurities and so forth, negligible for present purposes, as may have been present. As compared to these, a typical grey iron contained, combined carbon 0.23, graphitic carbon 3.08, and a typical pig iron contained, combined carbon .39, graphitic carbon 2.88 (this, as a matter of fact, the pig iron used in producing alloy As will be understood by those skilled in the art, the carbon content of cast iron varies in difi'erent types and therefore, the carbon content of the present alloy may correspondingly vary. It suflices that such content .fall substantially within the limits for cast iron, the invention having to do with an alloy with a cast iron base, and relating to the production of a cast iron of certain characteristics. Therefore, mention of carbon content in the claims is primarily for the purpose of indicating a castiron alloy. (As commonly understood of course cast iron has a carbon content in excess of 2% (say about 2.3% and ranging up to about 4.5%).

I claim:

1. An alloy, having major characteristics of cast iron, and containing manganese in amount giving the alloy a modulus of rupture substantially between 40,000 to 50,000 pounds per square inch.

2. An alloy, having major characteristics of cast iron, comprising? to 15% of manganese, in excess of 2% of carbon, and iron.

3. An alloy, having major characteristics of cast iron, comprising 3 to 15% of manganese, in excess of 2% of carbon and the remainder iron.

4. An alloy, having major characteristics of cast iron, comprislng about 9 to 10% of manganese, in excess of 2% of carbon, and the remainder iron.

5. An alloy, having major characteristics of cast iron, comprising iron primarily, manganese, and carbon in amount characteristic of cast iron, the manganese being sufficient in amount to give the alloy a modulus of rupture substantially between 40,000 to 50,000 pounds per square inch.

6. An alloy, comprising 3 to 15% of manganese, in excess of 2% of carbon, 1 to 5% of chromium, and the remainder iron.

7. A ferrous alloy containing-manganese from about. 13 per cent to 15 per cent, carbon from about 3 per cent to 4% per cent, and the balance preponderantly iron.

In testimony whereof I afiix my signature.

CHARLES B. JACOBS. 

